They are really fun! Although with the caveat that - as Rachel says in her review - the level of Period Typical Everything (mostly racism/colonialism) ranges from absolutely none, to easily ignorable, to "holy shit, W.E. Johns, wtf." The farther from England the books are set, the worse it typically is! But the war and spy ones (as opposed to the "Biggles explores strange lands full of savages" ones) are genuinely good. The things he does well, including action scenes, lush scenery descriptions, and batshit yet somehow plausible plots, he really does do very well, and I've really gotten attached to the characters in the dozen or so books I've read.